The ability to focus clearly and accurately on a point at a specific location relative to an individual is an important feature of human vision. Moreover, the ability to quickly focus on an object or visual indicia at a given distance from an individual, or to quickly shift visual focus from a first distance to a second distance, may be advantageous in a number of human endeavors. For example, a person who can quickly focus on one object and then change focus to another object may possess certain advantages over a person who can not change focus as quickly.
Both focusing and verging ability may be necessary to provide these advantages. For instance, a person may possess acceptable focusing abilities but lack acceptable vergence abilities. This may cause the appearance of two objects because the eyes have not verged sufficiently (although the objects will appear clearly focused). This may cause problems for the person in quickly and accurately detecting or following a fast-moving object, for example. Or, in an alternative example, a person may be able to verge his or her eyes on an object very quickly, but may not be able to quickly focus the eyes on the object. The object may thus appear blurry, although there will appear to be only one object as the person's eyes have verged on the object. This may cause difficulties in accurately distinguishing one object from another, for example. It may thus be advantageous to be able to measure and/or train a person's focusing and vergence abilities either separately or together. However, separately testing and/or improving focusing and vergence ability is a challenge because both skills are typically utilized together in visual tasks.
Superior visual focusing and vergence ability may prove advantageous, for instance, in various sports, athletics, leisure activities, or any number of human endeavors because a person who can focus and verge more quickly may be able to react more quickly or accurately to a visual stimulus or multiple visual stimuli. The ability to quickly shift visual focus and/or vergence may also be beneficial for a number of activities, such as driving. Given that visual focusing and vergence ability can be advantageous in various human endeavors, it can be beneficial to efficiently and accurately measure the visual focusing and vergence abilities of a subject to identify weaknesses in a subject's visual focusing and vergence abilities. Further, an individual may wish to improve his or her visual focusing and/or vergence capabilities, either to improve upon a weakness or to further enhance an ability.